The present invention relates to an optical pickup for recording and reproducing information in which light is convergently projected onto an optical recording medium to record information and the light reflected therefrom is photoelectrically converted to reproduce information and, more particularly, to an optical pickup using monochromatic light of a wavelength having excellent temporal/spatial coherence obtained from a general-purpose lamp which radiates light over a wide range of wavelengths, i.e., without employing a laser light source.
In an optical recording medium such as an optical disk, recording density is inversely proportional to the size of a light spot converged on the recording medium from a light source of a recording apparatus (optical pickup) via an objective lens. The diameter of the light spot is generally proportional to the wavelength of the light. However, the diameter of the light spot does not get infinitely smaller. For high-density optical recording, a light source of short wavelength having excellent convergence is being considered.
Generally, in this field, a laser apparatus is chiefly used as the light source. This is because a laser produces short wavelength light with excellent orientation and convergence. Further, lasers are monochromatic and easy to modulate.
However, below the wavelengths of green and blue light, it is difficult to develop a small laser apparatus. A conventional laser apparatus is large, and the driving thereof is complicated. Further, such lasers are very expensive due to low manufacturing yield and the employment of costly fittings and complex additional circuitry.